Technical Field
Embodiments generally relate to power management in computing platforms. More particularly, embodiments relate to adaptively disabling and enabling sleep states for power and performance.
Discussion
In order to reduce power consumption, mobile devices may opportunistically enter central processing unit (CPU)/platform low-power sleep states when the CPU becomes idle. For example, conventional mobile devices may be equipped with multiple CPU and platform sleep states (e.g., “Cx” and “S0ix” states, respectively), wherein the sleep states have different characteristics in terms of power, exit latency, and energy break-even time. Therefore, the ability of the device to maximally benefit from the presence of multiple sleep states may depend upon the ability of the device to select optimal sleep states at runtime.
Current sleep-state selection algorithms in the Linux family of operating systems (e.g., UNIX®, Solaris, FreeBSD®, etc.) may largely rely on predicted idle durations. It can be very difficult, however, to accurately predict idle durations for active mobile workloads. As a result, inaccurate idle duration predictions may often cause mobile devices to enter sleep states that are too deep, and as a consequence, wake up the CPU/platform before the energy break-even times of the selected states expire. Such “false entries” can result in even higher power consumption compared to staying in the active state. Too frequent false entries may therefore offset the potential power savings from entering low-power states, and ironically, even cause a net energy loss.